National Security Agency (NSA) director Alexander was the latest, and perhaps the most controversial, federal official to attend the annual hacker conference in Las Vegas to recruit warriors for battles being fought on the Internet.

“I am absolutely impressed with some of the stuff going on here,” Alexander said during a keynote presentation to a packed auditorium.

“In this room is the talent our nation needs to secure cyber space.”

His Def Con visit came after he was quoted by the New York Times as saying that between 2009 and 2011 there was a 17-fold increase in cyber attacks on critical US infrastructure such as power grids and mobile phone networks.

Along with being boss of the NSA, Alexander is an Army general and head of US Cyber Command created to defend against Internet-based attacks.